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Diving Safety

What is the Risk of Running Out of Gas?

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by Peter Buzzacott

Header photo by Kirill Egorov

See companion story: Why Do Divers Run Out of Gas?

In short, it is not known with any degree of certainty what the current risk is for running out of gas. Even so, for perspective, it may be possible to “guestimate” the probability within an order of magnitude. None of what follows would make it into any science or medical journal, but let’s look at some numbers purely for the purpose of having a conversation.

Between 1995-2004, Project Dive Exploration recorded 52,582 recreational dive profiles, made by 5,046 adult divers, an average of ten dives per diver.5 I’ll come back to that later. Complete data was obtained for 4,711 divers and running out of air was reported by 65 (1.4%) of those divers, or 1 in 72 divers. But, when estimating the frequency of something happening to people, it is customary to include a time component, such as “1 in 72 divers per year,” and in this case, we do not know how long each diver participated in the study. If they were all enrolled in the whole 10 years then we might say “1 in 720 divers, per year” (times 10 years would give 10 in 720, or 1 in 72, divers per year). Describing the risk or probability of running out of gas in these terms is how insurers work out what to charge for an annual premium, based on the risk per person, per year.

For divers, however, many of us are more interested in the risk per X-number of dives. Looking back at that average of 10 dives per diver over an unknown time period of participation in the study raises the question: how many dives does the average diver make each year? Well, between 2006-2015, a population survey company in Florida surveyed 383,389 people around the US, and those that dived reported making an average of ten dives each during the previous year.12 That might be accurate if, for example, most people only make a few dives each year but a small percentage make hundreds of dives every year. 

Photo by Julian Mühlenhaus.

The same study estimated that about 1.1% of the US adult population scuba dives each year, and that US divers make about 30-31 million dives each year.12 This introduces another grey area; not all those dives were likely made in the US, and also there are many dives made each year in the US by visiting international divers. So, it is not as simple as saying there are 30 million dives made by US divers each year in the US. We just do not know what that number is. 

Nonetheless, let’s forge onward with this exercise, in the interest of better understanding the issues preventing us from determining a firm estimate of risk. Among the 52,582 Project Dive Exploration dives, n=86 (0.16%) reportedly ran out of gas. Looking next at fatalities, in the last four DAN Annual Diving Reports there were 240 North American diving fatalities reported, 91% of those (219) were in the US or involved US divers.13-16 Of all the North American recreational diver fatalities, 16 were identified as either running out of gas at depth or else the mechanism of injury was “insufficient gas,” with (all else being equal) 15 of those (91%) likely to have occurred in the US or to have involved US divers.13-16 



What can we learn from the above figures? Well, not much, because of the vagaries I’ve already described; plus, the above studies were conducted in different locations, likely involved many divers not resident in the US, and spanned different time periods. Even if all the above related to US divers in recent times, that still wouldn’t mean the same conclusions could be drawn about divers from other countries. But, if we were to make a fanciful estimate, for example because we were desperate for a number, even a wrong number based on false assumptions, then this is what someone else might say [comments in square brackets highlight problems with each assumption]:

  • There could be ~30 million dives in the US each year [we don’t know this, but it might be true]
  • ~0.16% of these might run out of gas [we definitely don’t know if this is true, and it seems high to me]
  • This equates to 1 in every ~600 dives [again, seems high to me]
  • ~0.16% of 30 million equals ~49,000 times US divers run out of gas each year [seems like a lot to me]
  • There are, on average, ~4 out-of-gas fatalities in US divers each year [there are likely more, but not all fatality reports have complete data, so all we can say here is “at least 4 each year”]
  • If all the above were a true reflection of US recreational divers today, [which it is likely not], then on average US divers would run out of gas once every ~600 dives, but this would be fatal only once every ~13,000 times divers run out of gas [I’d suggest running out of gas may be fatal more often than this].
  • Regarding how often running out of gas results in injury, we have no data on this at all.

If nothing else, the above highlights that we need more data. We need prospective data from large dive operators, maybe air-integrated dive computer manufacturers, web-based dive log software managers, and recreational technical divers. If anyone reading this has useful data then I invite you to submit it for peer-review and publish it in a diving medicine or science journal. Until we get more data, please take the above with a grain of salt and consider it a conversation starter.

See companion story: Why Do Divers Run Out of Gas?


Dr. Peter Buzzacott MPH, PhD, FUHM, is a former PADI Master Instructor and TDI Advanced Nitrox/Decompression Procedures instructor, having issued >500 diver certifications. Today he is an active cave diver, holding various advanced cave diver certifications including advanced (hypoxic) trimix diver, and he is gradually gaining experience with CCR diving. To finance this, he conducts research into diving injuries and decompression/bubble modeling at Curtin University in Perth, Western Australia.

Cave

Close Calls: I Ripped My Drysuit a Kilometer Back In The Cave

It’s a potentially life-threatening equipment failure that most divers have thought but, but outside of minor leaks, few have experienced, and almost none have trained for. It certainly got the attention of photographer Fan Ping as he felt the chilly Florida spring water rush into his suit. Here’s how he survived the dive.

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By Fan Ping

🎶🎶 Pre-dive Clicklist: 平凡之路 (The Ordinary Road) by Pu Shu

Finally I had to say goodbye to my six-year old drysuit, in an unexpected way.

It was a cloudy day in January. There were not many people at Ginnie Springs in Florida as the temperature there was still too cold for the inflatable unicorns and flamingos with their masters in swimsuits that you see so often at the park. My friend Derek Dunlop and I met at the parking lot in front of Devil’s underwater cave system, and we started preparing for our photo shoot in Berman’s Room, at about 1006 m/3400 ft on the main line.

I sidemount my camera to the right.

As usual, we had first talked about the shooting plan with a storyboard and had decided to go in with six video lights since Berman’s Room is pretty big and fairly tall. Then we started preparing our rebreathers, but things did not go smoothly. Derek had a leak in his DSV, and then one of his O2 sensors stopped working for an unknown reason. Fortunately, he managed to fix both problems, but by then it was almost 2 pm already. I am a firm believer of ‘Rule of Three’ (If you have three major problems before you start the dive, then you should quit for the day), but I am also a photographer who was eager to capture the last piece of my Ginnie Springs project.

Berman’s Room
The Henkel

We got on our scooters and started diving. When I have many lights, I usually put two on the camera, which is side mounted on my right like a tank, two in my left thigh pocket, and the rest on my buddy. We dropped our own sidemount bailout tanks at Stage Bottle Rock at 1800’ and arrived at our destination 45 minutes into the dive as planned. We spent about 60 minutes playing with the lights and shooting, and then turned the dive happily at 105 minutes.

I was leading on the way out, riding in the high flow and thinking about the photos. When I passed the restricted tunnel before the Henkel restriction, the third problem of the day finally came. Scootering with the flow at perhaps  1 m/sec, the corner of my left pocket on my drysuit got caught on the tip of a rock and ripped a 3cm x 3cm hole. I could feel the chilly water flooding into my suit, so I stopped immediately, and within 10 seconds I lost my trim and buoyancy and was kneeling on the floor like in my Open Water class.

I told myself to “stop and think!” As in all the training we have done, I realized this was not an immediate life threatening situation, but the snowball could start rolling if I did not act correctly in a calm way. I checked my computers and used my primary light to get Derek’s attention and told him my drysuit was done for with the universal hand signal. Then I put some gas into the wing, but I was still on the floor. With more gas into the drysuit, I started moving again, in a vertical fashion. 

As you all can imagine, I had to put myself on the floor again at the Henkel. It is not extremely tight if you choose the right path, but with the DPV and camera and the Global Underwater Explorers (GUE)-configured JJ-CCR on my back, I was worried that I might not get out of the cave smoothly. Usually I stay very calm during a dive, but the depth was 32 m/105 ft, and the clock was ticking I was unsure of what would happen with that hole in my drysuit. I dumped all the gas in my suit and carefully crawled out of the restriction. Luckily, visibility is not a problem in Ginnie’s main tunnel because of the flow, and I can verify that a v-drill is easier when you have your belly on the ground.

To be honest, this was when I just completely got out of the panic mode. I knew I was getting closer to the surface, and I would be fine as long as I stayed focused. I inflated my suit, but as soon as I tried to stay horizontal, the gas leaked out from the hole. So, I put more gas into the loop and started being dragged by my scooter like SLAVE I in Star Wars, while still having to kick the whole time against the weight of my feet. 

That was when I started to feel cold. I could not imagine what this would have been like if I had been in a freezing cold cave like Orda, where the low temperature would have already killed me. All I could do was focus on scootering and choosing the taller passage if possible, in order to avoid messing with my buoyancy. Derek retrieved my bailout tank on the way out, and we made it back to the cavern in about 145 minutes, which is almost twice the time it usually takes.

My dive profile

There was no one else in the cavern when we started doing our longer-than-planned deco. I inflated my suit and knelt down on the rock at 6 m/20 ft so I could at least keep my torso relatively dry. I was getting colder and colder since I was not moving at all, but thanks to the 21ºC/70ºF degree spring water, my mind was still clear enough to think about getting a rental drysuit at Extreme Exposure and coming back in two days. After about 40 minutes of deco, we got back to the surface, and I had a really hard time walking back to my truck with all the water in my suit. What is worse, even the clouds started crying for me (or perhaps for my drysuit).

Drysuit full of water with the hole. Notice the rip on the top of the left pocket.

A fully flooded drysuit is something we always had talked about in our training but would never practice on purpose. When it actually happens, one can lose his trim and buoyancy within seconds, resulting in much more serious problems; for example, navigation, extended deco time, and hypothermia. 

In retrospect, I think there are 3 reasons why it happened to me:

  1. I was diving a Kirby Morgan M48 Mod-1 full face mask to facilitate better communication with my model, but the vision was relatively limited,and I did not pay enough attention to the surroundings;
  2. I had two big video lights in my pocket, and the pocket was exposed as I dropped my sidemount bailout tank;
  3. I should have gone slowly or maybe swum in more restricted areas.

I consider myself lucky that I got nothing but cold and lost nothing but an old drysuit, and thanks to Derek who made the process easier. It could have been a totally different story in another cave with a silty bottom or freezing cold water. However, out with the old, in with the new; it was time to get another drysuit.

Have you or a teammate ever had a “close call” while diving? Please take a few minutes to complete our new survey: Close Calls in Scuba Diving 


Fan Ping is a Chinese photographer and filmmaker based in Atlanta, Georgia, USA, and is dedicated to showing the beauty of the underwater world to people through his lens. He is specialized in combining artistic elements with nature and complex lighting skills in overhead environments, and this artistic style has brought him international acclaim, including awards from many major underwater photo/video competitions. You can follow his work on Facebook and Instagram: Be Water Imaging.

The best of Fan Ping’s work can be purchased at: www.bewaterimaging.com

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